Human interpretation of video or other imagery can be made difficult or even impossible by system noise, image blur, and poor contrast. These limitations are observed, for example, in most video and closed circuit television systems, and others, including such technology as RS-170 monochrome video, NTSC/PAL/SECAM video or digital color video formats.
Extreme lighting variation, for example, due to sunlight beams, can cause typical video cameras and imaging sensors to saturate (i.e., become unable to represent the real-world luminance range) resulting in wide-scale bright and dark regions having extremely low-contrast wherein objects are difficult or impossible to discern. At outdoor automated teller machines, for example, sunlight beams or strong lighting, in the background can cause a person in a dark area to become unidentifiable due to low contrast. This weakness is due to the limited luminance range of the imaging system.
The electronic iris and automatic gain control provided by some imaging systems are designed to try to optimally map the wide luminance values within a real-world light situation into a limited range digital representation, often resulting in a poor compromise. To adequately represent the bright areas, less illuminated areas become dramatically compressed in contrast and thus become very dark.
Besides having limited range, video or imagery from lower-cost imaging sensors can have significant noise due to a number of basic system limitations, as well as significant blur due to lower-cost, small, or simple optical configurations. Reducing noise and blur within these systems can improve the ability for a human viewer to effectively interpret image content.
Moreover, digital samples of interlaced analog video from a video field are typically taken by imaging systems. The noise inherent in such digital samples can make human interpretation of important details in the image difficult.
Hence, a need exists for a luminance range transformation apparatus and method that manipulates image data for improved interpretation thereof.
Others have provided some image post processing devices which can enhance contrast of an image. However, in many areas such as in security monitoring, real-time evaluation of images is highly beneficial or necessary. Accordingly, there is also a need to provide a luminance range transformation apparatus which can enhance an image in real-time or near-real time.